DESCRIPTION (taken from the applicant's abstract) Adrenal hypoplasia congenita (AHC) is a disorder of adrenal development associated with hypogonadotropic hypogonadism. Patients with the X-linked form of AHC have mutations in DAX1, which is expressed in the hypothalamus, pituitary, ovaries and testes, in addition to the adrenal glands, suggesting that DAX1 may have a role in regulating pubertal development. The DAX1 protein is a unique member of the nuclear hormone receptor superfamily. These proteins are transcription factors, exerting their effects through direct protein-DNA binding and through formation of complexes with other proteins. The broad objective of this study is to contribute to a better understanding of the function of DAX1 in adrenocortical development and regulation of puberty. The hypotheses are as follows. 1) mutations in the coding region of DAX1 may produce different clinical phenotypes, and understanding these will provide insight into the structure-function relationships in the DAX1 gene product; 2) DAX1 is a transcription factor that will regulate the expression of other genes; and 3) due to the presence of a putative zinc finger DNA binding domain, DAX1 may bind to a specific DNA sequence. To test these hypotheses we will pursue three Specific Aims: 1) identification of mutations in the coding region of the DAX1 gene among patients with AHC, and correlation of the mutations with patients' clinical phenotypes in order to gain insight into structure-function relationships in DAX1; 2) determination of which genes are regulated by the DAX1 protein; and 3) determination of the specific DNA binding sequence for the DAX1 protein. The Research Design and Methods that will be used include: 1) mutation analysis through single-strand conformational polymorphism analysis and/or direct sequencing of PCR fragments; 2) determination of the genes regulated by DAX1 protein by differential display of mRNA using a human adrenocortical carcinoma cell line; and 3) identification of a specific binding site for the DAX1 protein using mobility shift assays and PCR-assisted binding site selection from a pool of random-sequence oligonucleotides. The results of these investigations will better define molecular mechanisms by which DAX1 modulates adrenocortical development and the role of DAX1 in steroidogenesis and in the central regulation of puberty.